Microfluidic devices are used in an increasing number of applications: pharmacology, cell biology, genetics and biochemistry such as for instance for implementing polymerase chain reaction (frequently referred to as “PCR”). Microfluidic technologies enable the control and manipulation of fluids at a very small scale thereby reducing the cost of equipment and the volume of solution required.
It is known from WO 2014/056930, in the name of the applicant, to use droplet-based microfluidics for treating and analyzing a solution containing a biological material by (i) introducing said solution into microchannels of a microfluidic circuit; (ii) detaching drops of said solution in a carrier fluid, caused by the divergence of the microchannel walls, coupled with the effects of the surface tension of said solution; (iii) moving at least a portion of said drops in said carrier fluid to at least one drop storage zone in said microfluidic circuit caused by the divergence of said microchannel walls, coupled with the effects of the surface tension of said drops; (iv) applying a treatment to said drops situated in said storage zone(s); and (v) analyzing said drops situated in the storage zone(s).
One important issue for the development of microfluidic devices, such as that described in WO 2014/056930, is that sample introduction in the microfluidic device must be carried out in a reliable, accurate and convenient manner.
WO 2014/056930 describes introduction of a solution by adjusting the end of a pipette or the needle of a syringe in a supply hole before discharging the solution by pressing on the syringe or pipette.
US 2006/0163070 describes an apparatus for priming microfluidic device. Said apparatus comprises a carrier, having at least one reservoir, configured to receive a microfluidic circuit, wherein the reservoir is in fluid communication with the microfluidic circuit; and a priming unit comprising pressure applying means for applying pressure on the reservoir. Said pressure applying means comprises an outlet with an interface for contact with said reservoir.
Thus, the supply of samples in microfluidic devices commonly use pressure-driven pumping methods and requires an inlet port fluidly connected, by means of tubing, to actuators such as a syringe pump, a flow controller or a peristaltic pump. Said loading processes exhibits many drawbacks as they require (i) the knowledge of the precise location of the inlet port(s), (ii) one actuator and at least one connector for each inlet port and (iii) a complex assembly. Also, fluidic connections of the prior art increase the risk of cross-contamination between successive samples since connectors and samples are in contact or close proximity during priming of the microfluidic circuit.
Some contact-less loading methods have already been disclosed in the prior art to load the microfluidic circuit such as capillary action (Juncker D; et al., Autonomous microfluidic capillary system, Anal. Chem., 74 (2002), 6139-6144) or centrifugation (Ducrée J. et al.; The centrifugal microfluidic Bio-Disk platform, J. Micromech. Microeng. 17 (2007) S103-S115). However, said processes need to be optimized according to the physical properties of each fluid used (density, viscosity, surface tension) and cannot be used for two phase flows such as droplet formation.
It is therefore an object of the present invention to provide a universal contact less priming method for loading a solution inside a microfluidic device. Said contactless method may be carried out in a very simple manner by any operator, enables loading multiple devices with multiple fluids and thereby parallelization of the loading process (i.e. loading simultaneously at least two devices) and also avoids contamination due to the lack of physical connection.